1. Field of the Invention
This invention relates to a process for preparing a polyarylene thioether, more particularly to a process for preparing a polyarylene thioether with good efficiency under mild polymerization conditions.
2. Descriptions of Prior Art
The polyarylene thioether (hereinafter often referred to as PAT) such as polyphenylene thioether (hereinafter often referred as PPT) has hitherto been prepared by condensation polymerization of an aromatic dihalide and an alkali metal sulfide in a polar solvent at a high temperature under pressure.
However, this method has such problems that (1) an alkali metal salt remains in PAT and deteriorates the electrical properties of PAT and (2) a great amount of energy is consumed at a high cost.
On the other hand, a process for preparing PAT by the polymerization of a thiophenol is known from USSR Pat. No. 698,988. This process is industrially unadvantageous, because this process requires the use of a highly expensive catalyst such as MoCl.sub.5 /CF.sub.3 COOH. Furthermore, another process using sulfuric acid as a catalyst is known but this process has such a defect that a great amount of by-products, particularly cross-linked polymers is produced.